A single wafer epitaxial growth apparatus is known as a type of epitaxial growth apparatus. This apparatus forms an epitaxial film on the upper surface of a wafer by putting the wafer on a horizontal disc-like susceptor arranged in a horizontal heating furnace and allowing a material gas to circulate in a horizontal direction inside the furnace while rotating the wafer around a vertical axis. This apparatus is more frequently used with an increasing diameter of wafers and is considered to be mainstream in a 300 mm wafer compliant apparatus.
The single wafer epitaxial growth apparatus has a circular recess for placing a wafer provided on the upper surface of the horizontal disc-like susceptor for the purpose of bringing a material gas into contact with only the upper surface of a wafer on which an epitaxial growth film is formed. By allowing epitaxial growth by placing a wafer in the recess called counter boring, the sticking phenomenon of the wafer and the susceptor due to a growth film is suppressed.
The use of wafer using epitaxial growth includes power devices such as IGBT (Insulated Gate Bipolar Transistor) In the manufacture of epitaxial wafers for power devices, epitaxial growth films are thick, exceeding sometimes 100 μm or so. When such a thick film is formed, even if a wafer on the susceptor is contained in a recess, a sticking phenomenon of an inner circumferential surface of the susceptor and an outer circumferential surface of the wafer by a growth film spreading over both tends to occur. If this phenomenon occurs, a growth film of a sticking portion must be peeled off when the wafer is taken out from the susceptor after epitaxial growth. At this point, a considerable force is applied to an outer circumferential portion of the wafer and thus, cracks often appear in the wafer, leading sometimes to splitting.
A technology to provide a step in an inner circumferential portion on the upper surface of the susceptor recess as countermeasures to prevent the sticking phenomenon of a wafer and a horizontal disc-like susceptor is disclosed by JP-A 2004-327761 (KOKAI). According to this technology, the position of a wafer can be controlled to a center section of the susceptor recess so that an edge part of the wafer and the inner circumferential portion of the susceptor do not come into contact.
Basically one recess is provided on the upper surface of a horizontal disc-like susceptor in a single wafer epitaxial growth apparatus. On the other hand, a plurality of wafers can simultaneously be processed by arranging a large-diameter horizontal disc-like susceptor in a large horizontal heating furnace and providing a plurality of recesses around the rotation center of the upper surface thereof.